Mercury Complete Long Block Powerhead | OEM 8M0235085 | Fits Mercury 9.9HP 10HP 15HP 20HP 4-Stroke Outboards

Product Overview

Restore your outboard with this genuine OEM Mercury Complete Long Block Powerhead, designed for Mercury 9.9HP, 10HP, 15HP, and 20HP 4-stroke outboard engines. This factory long block includes the cylinder block, cylinder head, crankshaft, pistons, connecting rods, camshaft, and internal components, providing an excellent foundation for rebuilding your engine. Removed from a Mercury 20HP EFI outboard, this long block was carefully disassembled and inspected after a leaking head gasket caused approximately 20% lower compression on cylinder #2. Inspection revealed clean cylinder walls with no scoring, properly seating valves, and a camshaft free from scoring or abnormal wear. The rare OEM cylinder head is included, making this an excellent replacement or rebuild candidate. For best results, replace the head gasket, head bolts, and spark plugs before installation.

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Key Features

• Genuine OEM Mercury Complete Long Block Powerhead
• Fits Mercury 9.9HP, 10HP, 15HP & 20HP 4-Stroke outboards
• Includes cylinder head and internal rotating assembly
• Cylinder walls inspected with no scoring
• Valves seat properly
• Camshaft shows no scoring
• Hard-to-find OEM cylinder head included
• Ideal rebuild or replacement engine assembly
• Professionally inspected

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Technical Specifications

Specification	Details
Brand	Mercury
Product Type	Complete Long Block Powerhead
Condition	Used – Good Rebuild Candidate
Long Block Part Number	8M0235085
Replaces	8M0134425
Cylinder Block	8M0143240
Cylinder Head	8M0134432
Engine Type	4-Stroke
Compatible Horsepower	9.9 HP, 10 HP, 15 HP, 20 HP

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OEM Part Numbers

• 8M0235085 – Complete Long Block
• Replaces: 8M0134425
• Cylinder Block: 8M0143240
• Cylinder Head: 8M0134432

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Compatible Applications

Designed for select Mercury outboards including: Horsepower

• 9.9 HP
• 10 HP
• 15 HP
• 20 HP

Engine Type

• Mercury 4-Stroke

Important: Always verify compatibility using your engine's serial number and OEM part numbers before purchasing. If you need assistance confirming fitment, contact EZ Boats Marine and we'll be happy to help.

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Condition

This Mercury long block has been professionally inspected and is being sold as a rebuild-ready assembly. Inspection highlights include:

• Removed from a Mercury 20 HP EFI engine
• Complete long block with cylinder head and internals
• Cylinder #2 measured approximately 20% lower compression due to a leaking head gasket
• Cylinder walls are clean with no scoring
• Valves seat properly
• Camshaft has no scoring or abnormal wear
• Rare OEM cylinder head included
• Recommend replacing head gasket, head bolts, and spark plugs before installation
• Sold exactly as shown in the product photos

Please review all product photos carefully to evaluate the condition before purchasing.

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What's Included

Your purchase includes:

• OEM Mercury Long Block (8M0235085)
• OEM Cylinder Block (8M0143240)
• OEM Cylinder Head (8M0134432)
• Crankshaft
• Pistons
• Connecting Rods
• Camshaft
• Internal Engine Components

Not Included:

• Carburetors
• EFI components
• Intake system
• Fuel system
• Ignition components
• Starter
• Alternator
• External accessories

Only the components shown in the product photos are included.

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Shipping Information

Your long block will be professionally packaged to help prevent shipping damage during transit. We offer fast shipping throughout the United States, with international shipping available upon request. For an accurate shipping quote, please provide:

• Country
• ZIP or Postal Code
• Residential or Commercial Address
• Whether liftgate service is required

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Why Buy from EZ Boats Marine?

• Genuine OEM Mercury Marine Parts
• Professionally Inspected Components
• Factory Fit and Finish
• Honest Condition Descriptions
• Hard-to-Find OEM Components
• Fast Nationwide & International Shipping
• Secure Packaging
• Experienced Marine Parts Specialists
• Dedicated Customer Support

EZ Boats Marine is committed to supplying quality OEM marine parts backed by expert service and dependable support.

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Frequently Asked Questions

Is this a genuine Mercury part?

Yes. This is an original OEM Mercury Complete Long Block Powerhead manufactured by Mercury Marine.

What condition is it in?

The long block is in good used condition and has been professionally inspected. It was removed after a leaking head gasket caused reduced compression on one cylinder. The cylinder walls, valves, and camshaft are all in excellent condition with no scoring.

Which engines does it fit?

This long block fits select Mercury 9.9HP, 10HP, 15HP, and 20HP 4-stroke outboards. Always verify compatibility using your engine's serial number before ordering.

What is included?

The assembly includes the long block, cylinder head, cylinder block, crankshaft, pistons, connecting rods, camshaft, and internal engine components. External accessories such as carburetors, EFI components, and ignition parts are not included.

What should be replaced before installation?

We recommend replacing the head gasket, head bolts, and spark plugs before installing the engine.

Can EZ Boats Marine verify fitment?

Absolutely. Simply send us your Mercury engine's model and serial number, and we'll confirm whether this OEM 8M0235085 Complete Long Block Powerhead is the correct fit before you purchase.